Regge limit ($s\to \infty ,t\text{ fixed}$)

The Regge limit of a scattering amplitude takes the center-of-mass energy invariant $s$ large at fixed momentum-transfer invariant $t$. A leading trajectory produces a power $s^{\alpha (t)}$, with signature and residue factors. For the bosonic Virasoro–Shapiro amplitude in dimensionless string variables, $\alpha (t)=2+2t$. This differs from fixed-angle high-energy scattering.